Tools have been long known and used, which are installed to tire installing and uninstalling machines for removing tires from their rims, thereby facilitating the work of tire repairers.
A tire uninstalling and installing machine comprises a base with a substantially horizontal working table top installed thereto, which table top rotates about a perpendicular rotation axis, and has a series of clamps in diametrically opposite pairs, which are designed to be actuated to simultaneously move in centripetal or radial direction on the table top to hold or release an edge of a rim of a wheel that is laid by the tire repairer on the working table top for tire uninstalling or installing.
The tire uninstalling and installing machine also includes a column that extends upwards from the base and is integral with the latter, and carries a transverse arm whose free end facing towards the table top is equipped with a further arm facing towards the table top and substantially parallel to the column, which has connections for tire repairing tools.
Particularly, tire repairers encounter difficulties in uninstalling tires that have very low sides, typically tires for high-performance cars, or run-flat tires, that can roll even when they are deflated, without losing their directional ability.
These difficulties mainly arise because, when a wheel is locked on the table top, typically in a lying or substantially horizontal position, the space defined between the table top and the bottom side of a tire, or between the upper surface of the base and such side is very small, such that no working tools for removal of the tires from the rims can be introduced therein, which tools are actuated by actuators installed to the tire uninstalling and installing machines for this purpose.
A tire repairer can only use these tools after removing in a substantially easy manner the bead that rests against the upward edge of the wheel, and manually lifting with an auxiliary lever a downward portion of the bead until it overcomes the upper edge of the rim, by upwardly moving the whole tire and weight of the latter.
Only in this condition, there will be enough space for later introduction of a working tool known as a bead lifter between the base and the lead to be lifted, while it is being already held lifted by the tire repairer.
With the bead lifter introduced between the base and the side of the tyre, the thrust of the actuators that control the movements of the bead-lifting tool, with which the tire uninstalling and installing machine is equipped, may be used for the lower bead to fully pass over the upper edge of the rim, while the table top is rotated and the tire is lifted upwards out of its rim.
A feature required of these bead lifting tools is that they shall have a lifting path with a very gradual ascending profile, and a sufficiently large support surface for the sides and beads, to prevent any first upward pushing contact with the lower side of a tire from causing the latter to bend upwards and partially wrap the bead lifting tool, thereby affecting the effectiveness of the pushing action to pass over the upper edge of the rim.
In other words, these bead lifting tools are required to have a wide surface in contact with the side of the tyre, and also conformed to afford a progressive pushing action.
Prior art bead lifting devices may consist, for instance, of a pair of rollers supported by special movable position adjusting arms, which are placed in radial succession relative to the direction of rotation of the table top, to converge towards the center thereof.
The longitudinal axes of these rollers are maintained with different inclinations to create the required ascending path for progressively lifting the lower beads of the tires.
Once the bead lifting device has been placed next to the rim, and the portion of the lower bead that is manually lifted by the tire repairer has been laid on the first of the two rollers, the table top is rotated, whereupon the lifted bead progressively lies also on the second roller after passing over the upper edge of the rim.
Another embodiment of these prior art bead lifting devices uses a single roller supported with a substantially horizontal rotation axis at one end of a corresponding support arm that is movable relative to the table top.
This roller has the free end, designed to lie against the side of a tyre, with a frustoconical shape tapering away from the table top.
The outer edge of the roller forms a profile for contact with the tire beads whereas the outer tapering surface creates the desired progressive bead lifting profile.
As mentioned above, this prior art has the drawback of not allowing the use of a bead lifting device driven by drive members of the tire uninstalling and installing machine, from the very start of the process of lifting the lower bead of a tire of a wheel locked on the working table top.
A further drawback is that prior art bead-lifting devices often violently hit the edges of the wheel rims as they are positioned thereon, and are a danger for the integrity of rims.
Rims, especially those designed for installing low shoulder tires or run-flat tires are very delicate and expensive and any damage thereto will cause huge financial damages.
A further drawback is that proper positioning of bead-lifting devices is very uncertain, as the positioning area is substantially hidden to tire repairers' view by the wheels themselves, which obstruct the full view of this area and may cause errors by tire repairers.